One of the most highly recommended things to see in Mexico DF is the Anthropology Museum and I'd agree. Don't skip this one. There's also a nice gift shop with lots of good books and other cool things. And it's huge. I spent more than 4 hours in the place and felt like I was just barely able to go through everything. I could have spent twice as much time.
The museum is divided into different sections. You can start with the evolution part (and where I spent the longest, because I was with my middle son at the time and he loves that) and then move on to ancient Mexico cultures. There are two floors and the second floor usually had modern indigenous culture. Outside behind each of the different sections were models of various interesting structures.
I could post tons of photos again.